The appendicular muscles of Necturus maculosus. 399 



to extend at its proximal end so that it comes in contact with the 

 extensor ulnaris. It is divided into two portions, with origins in 

 contact but with distinct insertions. A large nerve (R. dorsalis 

 manus intermedius of Osawa?) passes between the two portions. 

 The details are as follows: 



a) Extensor radialis superficialis (ers). This portion 

 arises from along a longitudinal line upon the lateral condjie of the 

 numerus, higher up than any other muscle of the group; the lower 

 end is in contact with the origin of the humero-metacarpalis. Almost 

 as soon as the radius is reached the depest flbers of this portion begin 

 to insert along its free margin, and continue down the entire length 

 of the bone. The remaining fibers pass under the margin of M. 

 supinator, and insert in two bundles, into the marginal and dorsal 

 aspects of radiale and carpale II respectively. The most super- 

 ficial of the fibers of this muscle are the longest, and consist of 

 those that insert into carpale II; beneath these lie the fibers that 

 insert into the radiale, and the deepest of all are those that insert 

 into the radius. 



b) Extensor radialis profundus (erp). This portion lies 

 medial to the former and is wholly covered by the humero-meta- 

 carpalis. It arises from the lateral condyle of the humerus, along 

 a transverse line just distal to and parallel with that of the latter 

 muscle. This origin, tendinous at first, becomes muscular almost 

 immediately and the fibers insert along the greater part of the 

 ulnar margin and more than the ulnar half of the dorsal aspect of 

 the radius, including in length the most of its shaft. 



M. supinator (s). This muscle is easily distinguished since 

 it is the only one on the dorsal aspect of the limb that is obliquely 

 placed. The terminal portion alone is superficial and may be seen 

 eraerging from beneath the humero-metacarpal upon the radial side; 

 the remainder is concealed by this latter muscle, which must be 

 removed in orcler to expose it. It is a shorter muscle than its 

 homolog in the leg, and lacks entirely an origin from the ulna 

 (corresponding to that from the tibia), but its two other origins 

 from the carpal bones correspond exactly to those from the tarsus. 

 The muscle thus arises by superficial fibers from the radial margin 

 and a bit of the dorsal surface of the ulnare-intermedium, and by 

 a deeper slip from the centrale, these latter being best exposed by 

 cutting through the muscle near its insertion and reflecting it. The 

 muscle is inserted by a tendon into the radial margin of meta- 



